Display scheme for decompression data

ABSTRACT

Novel display scheme for decompression data is herein presented which can be animated by various types of decompression computers and permits the use of new, highly advantageous procedures in many aspects of diving, notably: (1) no-decompression diving, (2) decompression diving, and (3) repetitive diving. It allows a diver to choose his margin of safety, lending itself to use by divers predisposed to DCS, or by divers working under arduous conditions. It consists of graphical and digital display elements which accesses the contents of a microprocessor or other information source as to a diver&#39;s tissue&#39;s state of saturation with inert gas. This information is presented to a diver in a simple, straight forward and non-confusing manner which allows him/or to use the new highly advantageous procedures.

This is a continuation of U.S. application Ser. No. 219,015, filed July14, 1988, now abandoned, which was a continuation of U.S. applicationSer. No. 786,723 filed Oct. 15, 1985, now U.S. Pat. No. 4,782,338, whichwas a continuation of application Ser. No. 648,797 filed Sept. 7, 1984,now abandoned which was a continuation of U.S. application Ser. No.341,281 filed Jan. 21, 1982, now abandoned.

A. FIELD OF THE INVENTION

This invention is a unique display scheme that allows informationcontained in certain types of decompression computers to be communicatedunder circumstances where such information was previously unavailable.This invention makes possible a substantially different and much refinedprocedure for decompression and for no-decompression diving.

B. PRIOR ART

Knowledge as to the amount of N₂ or inert gases in general dissolved inthe fluids and tissues of the human body is of great importance inavoiding DSC (decompression sickness) or the "bends".

Various devices have been known which, using mathematical or analogsimulators, attempt to track the [N₂ ] changes which occur during thecourse of an underwater dive or any hyperbaric exposure. (U.S. Pat. Nos.3,457,393; 3,681,585; 4,005,282; 4,054,783; 4,192,001).

According to man's present, incomplete understanding of thedecompression phenomena, inert gases in the breathing mixture are takenup or released in a more or less exponential fashion whenever adisequilibrium exists between their concentration in body tissues andtheir concentration in the inspired gas. The half-times for this uptakevary with the particular body tissue or fluid. The number of "tissuecompartments", as they are called, is unknown and in fact there may notexist discreet compartments. Present day decompression practices arebased on the assumption that there are in the neighborhood of 6 tissuecompartments controlling the duration of man's hyperbaric excursions.

Each tissue (of a half time in range of 5 to 200 minutes for example) isthought to be able to tolerate a certain level of supersaturation withinert gas without forming the small bubbles which cause DCS. Thiscertain level is known as the M value. The object of decompressionpractice, whether it be guided by tables or computing devices, is tonever exceed this permissible supersaturation for a given tissue. (Itmust be noted here that there exist other schools of thought concerningthe matter of permissible supersaturation, but at present, decompressionpractices which give satisfactory results (within their limitations) arebased on the theory outlined above.

Modern decompression computer may keep track of approximately 10hypothetical tissues. The information they display, however, isgenerally restricted to (1) the current depth, and (2) the depth towhich a diver can currently ascend without exceeding the permissiblesupersaturation of any one of the n tissues being monitored. There existprocedures wherein this information is used to safely attain the surfaceafter completing his task or purpose underwater.

There is a great deal more information contained in the decompressioncomputer than is displayed to the user. The reasons for this limitedquantity of information displayed are, in part, that (1) it is notapparent of what value this further information would be to the diver inhis effort to avoid DCS, (2) an excess of information may serve only toconfuse a diver, increasing risk of diver error, and (3) displayingsupplemental information via the standard digital technique is notpossible without greatly enlarging the UDC, which is undesirable for adiver-carried device.

The present invention presents a solution to these three objections. Itis greatly superior to present display schemes in allowing a diver tostay within his no-decompression limit (i.e. diving such that he canalways ascend directly without having to stop or alter his ascent tode-gas). It also permits a refined decompression procedure to befollowed, resulting in faster and safer total ascent time.

C. OBJECT OF THE INVENTION

It is an object of the invention to provide a diver-carried method ofdisplaying information concerning a diver's state of saturation withinert gas so that he may more effectively avoid the bends.

It is a further object of the invention to provide this information in asimple, compact, straightforward, and non-confusing manner.

It is yet another object of the invention to provide a diver withinformation and a method for its interpretation which will enable adiver to optimize his dive profile for maximum usable time underwater.

It is a further object of the invention to give a diver an easilyapprehended conception of his margin of safety, and to allow him easilyto choose his margin of safety in accordance with the numerous factorssuch as fatique, obesity, etc. which predispose a diver to the bends.

It is another object of the invention to allow the optimization of thedive profile for no-decompression diving, a special interest of sportdivers.

It is yet another object of the invention to permit a refineddecompression procedure to be followed which results in a faster andsafer total ascent time.

D. DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a preferred embodiment of the invention including LCDmatrix, multiplexor and RAM storage in block diagram form.

FIG. 2 depicts an alternative embodiment of the invention with dotmatrix rows, decoder and RAM storage in block diagram form.

FIG. 3 depicts diagrammatically part of an LED display device.

E. DETAILED DESCRIPTION OF THE INVENTION

In the preferred embodiment of this invention, the degrees of saturationwith inert breathing gas in the body tissues are displayed graphically,and depth and ceiling are displayed digitally. The depth is displayedgraphically between 0 and 99 f.s.w. (feet of seawater). The tissuepressures are also displayed as equivalent depth in f.s.w., arranged inorder of ascending half-times. A curve traced on the display marks thecorresponding M value for the tissues considered.

LEDs (FIG. 2) or a number of other media can be used to construct thisdisplay, but a multiplexed LCD matrix (FIG. 1) is advantageous becauseof high information density, long life, low cost, and low powerconsumption. The high information density LCD used in the preferredembodiment allows upward of ten tissues to be displayed. This reducesthe display to a surface which advances or retreats from its origin (asthe degrees of saturation in the n tissues varies). The changing profileof this surface and its spatial relation to the M value linecommunicates to a diver, at a glance, the status of the sum of his bodytissues, and concurrently his needs for decompression. If any part ofthe surface is seen to cross the M line, the diver is in need ofdecompression. The ceiling depth will indicate what is the minimum depthto which he can safely ascend. At this ceiling depth, inert gaselimination will proceed at the maximum safe rate. A diver wishing toascend in the minimum possible time would "hang" at the ceiling depth,continuously matching his depth to the ceiling, until the ceilingreaches 0 f.s.w. at which point he could exit the water. A diver who,for a number of reasons, might wish to add to his own safety margin,would decompress by initially ascending to a depth below the permissibleceiling, 10 feet for example, then continuously maintaining his depth at10 feet below the ceiling. He can exit the water when the ceilingreaches 0 f.s.w.

The graphical portion of the display allows the diver to accuratelyestimate his required ascent time, because he can readily see whichtissue group (a slowly equilibrating versus a quickly equilibrating) isresponsible for his need for decompression.

In the preferred embodiment of the invention, when driven displaysegments extend beyond the M value line, these and all segment sectionsbetween these and the origin will flash continuously. This alerts theuser of the need for decompression. Alternate embodiments include anaudible alarm and colored indicator lights.

The effectiveness of the invention in conducting multilevelno-decompression diving is much greater than previously available:

The multitude of bars that make up the surface representing the body'snitrogen profile are constantly changing, each bar tending toward thecurrent depth at its own (half-time) rate. No-decompression diving isaccomplished by keeping all bars in the area between the origin and theM value line. To do this, the diver/user makes a simple comparison whena certain tissue group(s) nears the M value line. The tissue group inquestion will always tend toward the current depth, which is graphicallydisplayed adjacently to the tissue groups. Thus the diver can controlthe position of the bar simply by changing his depth. In the case ofno-decompression diving, he would move to a depth above thenear-critical tissue pressure, causing the corresponding bar to retreatback toward the origin. Additionally, he knows what the response timewill be for this retreat since fast half-time tissues equilibratequickly and slow half-time tissues do so slowly.

The effectiveness of the invention in repetitive dive planning is muchgreater than previously available means: During a surface interval, themeter is left running. Thus prior to a repetitive dive a diver knows ata glance the status of all of his tissues and can accordingly choose anoptional dive profile for the repetitive dive.

In addition to the above described methods of interpreting and usingthis invention, a user develops an "intuitive" understanding of it infamiliarizing himself with this display scheme, which allows him toconceive further beneficial strategies of a subtler nature for its use.

The following description is presented with references to theaccompanying figures to aid in its comprehension.

FIG. 1 illustrates a possible embodiment of a UDC, represented bymicroprocessor 12 with RAM storage 14, coupled with the novel displayscheme. In this embodiment the display is composed of 3 liquid crystalcomponents 26, 28 and 30, and a decoder/multiplexer 22. The three LCcomponents 26, 28 and 30 may be integrated into a single device, or maystand separately. The three separate components shown 26, 28 and 30 areconnected with the decoder/multiplexer 22 through lines 32, 34 and 36,respectively.

Ten RAMs (R0-R9) representing the amount of dissolved gas in bodytissues are made available to the decoder by the microprocessor 12. Thisinformation may be in the form of an 8 digit binary number. Ten RAMsrepresenting the status of R0-R9 with respect to the M value for thattissue are also made available to the decoder. As was previouslyindicated, a curve 38 on a display 26 marks the corresponding M valuesfor the tissues considered. This information is in the form of a singlebit, Sn=1 for Rn>=Mn, and Sn=0 for Rn<Mn (2). (In embodiments where moreor fewer tissues are modeled by the microprocessor, there arecorrespondingly more or fewer RAMs Sn and Rn).

A RAM, P, representing the current ambient pressure in terms of f.s.w.from a pressure transducer 18 coupled with the microprocessor 12 throughline 20, and C, representing the ceiling depth, are also made availableto the decoder as 8 bit numbers.

The elements R0-R9, S0-S9, P, and C are revised periodically, on theorder of one second, by the microprocessor 12. At the end of each timeperiod, the revised values are sent to the decoder/multiplexer 22 online 24, which thus decodes, multiplexes and displays the informationcontained on these RAMs in the following manner:

P is displayed as an integer between 0 and 255 on a standard 3 digit, 7segment LCD 28. C is likewise displayed on LCD 30.

P is additionally displayed on the graphical component 26 as are thevalues for R0-R9. Each of these 11 RAMs are allowed a track on thegraphical component, extending vertically downward as depicted inFIG. 1. In the preferred embodiment, the tracks are composed of 99segments to display depths/pressures of up to 99 feet. For moredemanding diving, involving greater depths and exposure times, moresegments allowing greater depths/tissue pressures may be utilized.

For example when R0 is binary 100001, equivalent to decimal 33, thetrack corresponding to R0 will display this fact by driving segments 1through 33. When P=binary 1010101, decimal 85, the track correspondingto P will display the segments 1 through 85, and additionally the 3digit 7 segment display will display "85". If P should exceed 99, thisfact would be reflected by the 3 digit display. All 99 segments of the Ptrack are driven at values were P≧99. When Rn≧Mn then Sn=1 and allsegments of the track corresponding to the Rn blink continuously,informing the user of this state.

The display may also be constructed using commerically available dotmatrices. This practice yields lower resolution; however, satisfactoryresolution to convey the essential information intended by the inventioncan be obtained through the use of a 32×32 dot matrix 26' such asCrystalloid Electronics SX 402. This may be driven by a Hughes 32×32 LCDmatrix decoder/driver 22' coupled with microprocessor 12' through 24'.RAM storage 14' representing R0-R9, S0-S9, P and C, and M value line 38'are also indicated. In this embodiment, scaling is necessary in order toallow 32 segments of track to represent 99 (or more) feet of depth. Insuch an embodiment a maximum of up to 31 tissues may be represented,leaving one track to depth and the adjacent track as a "spacer" to setoff depth from tissue pressures. Matrices having lower resolvingabilities are unadvisable since the "area" quality as well as theaccuracy of the information displayed deteriorates with such coarsermatrices. The waveforms to drive the display may be generated by themicroprocessor 12' itself, instead of the external decoder/multiplexer22 of FIG. 1.

An alternate embodiment of the invention involves substituting anarrangement of LEDs for the LCD components of the preferred embodiment(FIG. 2). Such an embodiment has the advantage of high legibilityunderwater. Its higher energy consumption and lower information densityrelative to the LCD embodiments keep these latter the preferred forms ofthe invention.

An edge on view of a single track 126 of such an LED embodiment, withLED's 128 coupled through a conductive substrate 130 to electricalconnectors 132 is shown in FIG. 3.

Another alternate embodiment of the invention is to construct thegraphical and other display components using a Lisa (Light SwitchingArray). A Lisa's very low power consumption and non-volatility indicateits potential to replace LCD elements in the preferred embodiment.

Yet another embodiment of the invention may be constructed using anelectrochromic display.

An alternate embodiment to the digital microprocessor embodiments thusfar discussed is to construct the device using analog circuitry togenerate voltages reflective of Rn and to either (1) convert theseanalog signals into digital signals for display, or (2) to construct amechanical analog of the digital device such as ferromagnetic cursorsmoving in magnetic fields generated by the analog voltages.

Alternate embodiments of the graphical portion of the display may beconstructed by passing it through a variety of geometricaltransformations, such as inverting it, or bending it into a circle suchthat the origin is at the center and the bars radiate outward toward thecircumference.

When more than one inert gas is used in the breathing mixture, anadditional graphical component is needed for each additional inert gasin order to properly display the diver's decompression status.

This invention may also be used by divemasters or other diving supportpersonnel monitoring a submerged diver with a suitable means of datatransfer from diver to support crew.

GLOSSARY

Decompression Diving--The practice of planning diving excursions of suchdepth and durations that immediate ascent following completion of theworking portion of the dive is not possible without risking the bends.This practice permits greater working time, but regulated ascentprocedures must be followed to allow adequate de-gassing prior tosurfacing.

No-Decompression Diving--The practice of planning diving excursions ofsuch depths and durations that ascent to the surface may be made at anytime during the dive. The form of diving most often practiced by sportdivers.

Dive Profile--A diver's depth versus time during the course of a dive.

Ceiling--The shallowest depth to which a diver may safely ascend withoutover-supersaturation occuring in any tissue.

M Value--A tissue's coefficient of that same tissue's permissiblesupersaturation with an inert gas.

Repetitive Dive--Any dive made within 12 hours of a previous dive.(After 12 hours the body is considered to have completely lost anyexcess inert gas.)

The possible embodiments of the invention are given for illustrativepurposes only, and it is understood that the invention may be practicedin other forms without departing from its true spirit. Thus theinvention should be limited only by the language of the followingclaims.

What is claimed is:
 1. A portable device for displaying decompressiondata comprising:a pressure sensor for sensing ambient pressure and forgenerating a signal representative of the sensed pressure; a programmedcomputer for receiving pressure signals from the pressure sensor and forperiodically generating data representative of the level of dissolvedgases in each of a plurality of tissue models having differingsaturation half-times; memory means for periodically receiving andstoring the dissolved gas level data for each of the tissue models andinformation concerning a predetermined dissolved gas level limit foreach of the tissues modeled; and display means, including a graphicdisplay device for receiving and simultaneously displaying the dissolvedgas level data for one of the tissue models and the predetermineddissolved gas level limit information for the displayed tissue model. 2.The device as recited in claim 1 wherein the display means permits theuser to gauge the maximum allowable rate at which the ambient pressuremay be reduced without the dissolved gas level of the displayed tissuemodel exceeding its dissolved gas level limit.
 3. The device as recitedin claim 1 wherein the displayed tissue model the tissue model having adissolved gas level which at the existing ambient pressure will exceedits corresponding dissolved gas level limit in the shortest time period.4. The device as recited in claim 3 wherein the programmed computerdetermines the time remaining until the dissolved gas level of thedisplayed tissue model exceeds its corresponding dissolved gas levellimit at the ambient pressure and the display means receives anddisplays the determined time.
 5. The device as recited in claim 1wherein the dissolved gas level limit for each tissue model is themaximum level of gases which may be dissolved in the particular tissueto permit movement to surface pressure without the need fordecompression.
 6. The device as recited in claim 1 wherein the dissolvedgas level limit for each tissue is the tissue's M value.
 7. The deviceas recited in claim 1 wherein the display means identifies the tissuemodel being displayed to permit a user to estimate the rate of change ofthe dissolved gas level for the displayed tissue model.
 8. A portabledevice for displaying decompression data comprising data generationmeans for generating dissolved gas level data for a tissue model andgraphic display means for receiving and simultaneously displaying anindication of the level of dissolved gases in a tissue model and apredetermined dissolved gas level limit for the displayed tissue modelto permit the user to gauge the allowable rate at which ambient pressuremay be reduced without the dissolved gas level for the displayed tissuemodel exceeding the dissolved gas level limit.
 9. A method to be used bya diver for determining decompression information from a graphic displaydevice which simultaneously displays the level of dissolved gases intissue model and a predetermined dissolved gas level limit for thetissue model displayed, comprising periodically observing therelationship between the dissolved gas level for the displayed tissuemodel and its dissolved gas level limit to determine whether thedissolved gas level for the displayed tissue model has exceeded itsdissolved gas level limit and, if not, observing the rate at which thedissolved gas level for the displayed tissue model is approaching itsdissolved gas level limit to establish the time remaining untildecompression is required.
 10. A portable device for displayingdecompression data comprising graphic display means for receiving andsimultaneously displaying an indication of the level of dissolved gasesin tissue model and a predetermined dissolved gas level limit for thedisplayed tissue model to permit the user to gauge the allowable rate atwhich ambient pressure may be reduced without the dissolved gas levelfor the displayed tissue model exceeding the dissolved gas level limit.